1. Field of the Invention
The present invention relates to a communication system that includes a relay device for a relay of information among different communication buses. In particular, the present invention relates to a communication system capable of properly controlling power supply of the system while simplifying the configuration of a control device for controlling devices based on information to be relayed, a relay device constituting the communication system, and a method for controlling power supply of devices in the communication system.
2. Description of Related Art
In the technical field of vehicle control, the configuration in which several electronic control units (ECU) for respectively controlling devices mounted in a vehicle are connected by communication buses to transmit/receive information mutually for executing various processing is commonly used. Since the number of ECUs connected to a communication bus is limited or a communication speed is varied according to the function of an ECU, a configuration is adopted in which ECUs are divided into a plurality of groups, each of which is connected to a communication bus, and a relay device (gateway) is connected between different communication buses.
With a communication system including a relay device, each communication device transmits an information group of multiple pieces of information based on a communication protocol, and a relay device receives the information group collected and transmitted from each communication device and achieves a relay by determining whether or not the information group without modifications thereto is transmitted to another communication bus.
Specifically, in a case where a CAN (Controller Area Network) is generally used in a communication system related to vehicle control, each ECU stores signal information obtained from devices in the data part of a CAN message identified by CAN ID and collectively transmits the information. A relay device refers to a routing table stored for each CAN ID that specifies the necessity of a relay and a communication bus being a relay destination for each CAN message received and transmits a CAN message required for a relay to the communication bus being a relay destination, relay processing is achieved by a message routing function for transmitting the received CAN message without modifications thereto.